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New therapy targets a patient's unique cancer

One of the biggest threats to health is cancer. And in the battle against the disease, there is a promising new tactic. It dispenses with the "one-size-fits-all" approach and tailors the treatment to the patient. CBS News correspondent Dr. Jon LaPook looks at this latest development.

When Sheila Gallant was diagnosed with breast cancer nearly four years ago, it had already spread to her bones, liver and lungs. Chemotherapy and radiation caused her hair to fall out and made her sick. But worst of all, the treatment stopped working.

Her team at Massachusetts General Hospital (MGH) offered her an experimental treatment based on a profound change in thinking: that each person's cancer is unique.

"Every patient will receive a different therapy that is more active," said Dr. Jose Baselga, chairman of oncology and one of Gallant's doctors, "that is less toxic, that will improve the quality of life and will improve their survival time is what we're doing here. It's extremely exciting. It's a whole new game here."

Here's how the game has changed: Researchers have identified hundreds of different genetic defects or mutations that help make each cancer unique. The idea is to identify a specific mutation and find a drug that targets it.

In breast cancer, more than 100 mutations have been discovered. These mutations lead to defective proteins that make the cells replicate out of control. Targeted drugs hone in on those proteins and disable them, killing cancer cells while leaving healthy ones alone.

"By identifying what drives every single tumor," said Baselga, "we now can begin to have better therapies that are smarter."

MGH uses the world's largest library of tumor cells to study mutations and test new drugs.

"What we've done here is set up a system that can detect the presence of 91 different mutations," said Dr. Mark Kris, chief of the lung cancer department at Memorial Sloan-Kettering. He acknowledges only a small percentage of tumors have a mutation with a known treatment. And even effective targeted drugs may only work in a fraction of patients.

In Gallant's case, doctors found a breast cancer mutation they could target with an experimental pill. She's been taking it for two months with no side effects so far. She's having regular PET scans to see how well the treatment is working -- and tumors in her breast, liver and lungs are shrinking.

What went through her head upon seeing the results?

"Amazing," she said. "Totally amazing. How it was there before and all of a sudden it's not there anymore? I find myself very fortunate to be here and that they picked this drug for me."

That's definitely an impressive early response, but there is at least one concern for patients like Sheila Gallant: Cancers that seem under control can develop new mutations that make a therapy stop working. That's why researchers are constantly trying to find new targeted drugs, so they'll have a backup plan if needed.